Power train and power transmission therefore

Abstract: The present invention relates to a power transmission (10) that is interposed between the internal combustion engine (11) and the drive ratio selection transmission (39) of a vehicle. A motor/generator (14) is operatively connected to the power transmission, and the power transmission selectively adds and subtracts torque provided by the motor/generator to the torque provided by the internal combustion engine. The power transmission effects the operative interconnection between both the internal combustion engine and the motor/generator to the drive ratio selection transmission. The power transmission employs compounded first and second planetary gear sets (19,21). A common gear member (16) serves not only as the ring gear for the first planetary gear set but also as the sun gear for the second planetary gear set. The power transmission provides operating advantages not possible with prior art mechanisms, and these advantages allow the internal combustion engine to operate with desirable engine emissions.

Description: The present invention relates to a power transmission for a power train for a vehicle. More particularly, the present invention relates to a vehicular power transmission that is capable of receiving input torque from both an electric motor and an internal combustion engine. Specifically, the present invention relates to an integrated hybrid power transmission that is operatively connected to an integral electric motor/generator that not only starts the internal combustion engine but also augments a friction starting clutch with electrically generated torque and/or electric motor inertia torque for launching movement of the vehicle. The present invention relates to power transmissions to co-ordinate the torque output of an electric motor/generator and an internal combustion engine to a drive ratio selection transmission, and especially, to planetary gear sets and the associated torque transfer devices utilised for providing the desired interaction between the internal combustion engine and the electric motor/generator to meet the economic and emission requirements of internal combustion engines to propel vehicles. DE-A-3842631 describes a power transmission as in the pre-amble of claim 1. FR-A-2200800 describes a power train including a power transmission interposed between an engine and a drive ratio selection transmission; and a motor/generator. Motor/generators have heretofore been employed for launching vehicles. However, the prior art has not appreciated, and has not therefore, disclosed how an integrated motor/generator can be incorporated in the overall operation of a vehicle for maximum utility. It is, therefore, an object of the present invention to provide a power transmission wherein the power train provides a greater electrical generating capacity from a motor/generator than is currently available with belt-driven generators. To this end, a power transmission in accordance with the present invention is characterised over DE-A-3842631 by the features specified in the characterising portion of Claim 1. The present invention preferably provides an integrated hybrid power transmission, as above, that utilises the inertia available from the electric motor/generator to assist in the vehicle launch. The present invention may also provide an integrated hybrid power transmission, as above, that reduces the rate at which the speed of an internal combustion engine is changed during vehicle launch, unlike conventional prior art systems, wherein energy was dissipated to accelerate the internal combustion engine and all components driven thereby, to reach a power range suitable to launch the vehicle before launching could be effectively achieved. The present invention may further provide an integrated hybrid power transmission, as above, that permits the vehicle to be driven by either the electric motor/generator or the internal combustion engine, or by both. Still further, the present invention may provide an integrated hybrid power transmission, as above, that permits a silent engine start and no engine load in idle condition. Further still, the present invention may provide an integrated hybrid power transmission, as above, that permits the motor/generator to be used for regenerative braking. Additionally, the present invention may provide an integrated hybrid power transmission, as above, that can be employed in conjunction with either automatic or manual drive ratio selection transmissions to replace the engine starter, the electric generator (or alternator), the torque converter or the standard starting clutch. Even further, the present invention may provide an integrated hybrid power transmission, as above, that can be employed to provide two torque ratios for the electric motor/generator, three torque ratios for the internal combustion engine and variable speed ratios for both. In general the present invention relates to a power train for a vehicle having an internal combustion engine to provide a torque source and a drive ratio selection transmission. The power train includes a power transmission that is interposed between the internal combustion engine and the drive ratio selection transmission. A motor/generator is operatively connected to the power transmission, and the power transmission selectively adds and subtracts torque provided by the motor/generator to the torque provided by the internal combustion engine. The interconnection provided by the power train between both the internal combustion engine and the motor/generator to the drive ratio selection transmission is accomplished by a power transmission. The power transmission employs compounded first and second planetary gear sets. The first and second planetary gear sets each have a sun gear, a ring gear and a plurality of planetary gears. The planetary gears are mounted on respective first and second carriers operatively to connect the sun and ring gears of the respective planetary gear sets. Although conventional compounding of the planetary gear sets may be employed, it should also be appreciated that a common gear member may serve not only as the ring gear for the first planetary gear set but also as the sun gear for the second planetary gear set. The internal combustion engine is adapted selectively to provide torque to the ring and carrier of the second planetary gear set. Means are also provided selectively to transfer torque between the motor/generator and the sun gear of the first planetary gear set and the second carrier. Further means selectively transfer torque between the drive ratio selection transmission and the internal combustion engine, the ring gear of the second planetary gear set and the motor/generator through the second carrier. The first carrier is selectively connected to ground, and means selectively connect the drive ratio selection transmission to ground. The improved integrated hybrid power transmission provided by the present invention is operative to add or subtract torque from the motor/generator to torque from the internal combustion engine in order to provide the most favourable fuel economy and/or emissions control. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a schematic sectional representation of a power transmission in accordance with the present invention operatively connected to an electric motor/generator and an internal combustion engine to provide torque, through a drive ratio selection transmission, to the final drive of a vehicle; Figure 2 is an enlarged schematic plan view of the compound planetary gear set particularly adapted for use in conjunction with the power transmission of Figure 1 taken on the line 2--2 of Figure 1; Figure 3 is a diagrammatic representation -- commonly referred to as a "Lever Analysis" -- of the compound planetary gear set of Figure 2, depicting the compound planetary gear set for Engine Start Mode; Figure 4 is a diagrammatic representation similar to Figure 3 depicting the compound planetary gear set for Vehicle Launch Mode; Figure 5 is a diagrammatic representation similar to Figures 3 and 4 depicting the compound planetary gear set for Motor/Generator Coupling Mode; Figure 6 is a diagrammatic representation similar to Figures 3-5 depicting the compound planetary gear set for Internal Combustion Engine Coupling Mode; Figure 7 is a diagrammatic representation similar to Figures 3-6 depicting the compound planetary gear set for Regenerative Mode; Figure 8 is a diagrammatic representation similar to Figures 3-7 depicting the compound planetary gear set for Electric Only Mode; and Figure 9 is a diagrammatic representation similar to Figures 3-8 depicting the compound planetary gear set for Reverse Mode. With reference to the drawings, and particularly Figure 1, an (integrated hybrid) power transmission, generally identified at 10, receives input torque from an internal combustion engine, schematically identified at 11, in a vehicle (not shown) as well as from a rotor 12 that is rotatable relative to the stator 13 of an electric motor/generator, identified generally at 14. The power transmission 10 employs a compound planetary gear set that is identified generally by the numeral 15 in Figures 1 and 2. An oil pump 17 is customarily operated by the internal combustion engine 11 of the vehicle to provide hydraulic fluid under pressure for lubrication and also for actuation of the several hydraulic devices that are customarily employed within vehicle transmissions. In the present arrangement, however, the oil pump 17 may be operated by the electric motor 14 or other driving source such as, for example, a separate electric motor, in order to provide hydraulic power even when the internal combustion engine 11 is not operating. The hydraulic devices, as well as the lubrication systems, are well known to those skilled in the art and will not, therefore, be further described herein. The compound planetary gear set 15 utilises a common connecting gear 16. The radially inner surface of the connecting gear 16 is provided with a plurality of teeth 18 that allow the connecting gear 16 to serve as a ring gear in a first planetary gear set 19 in the compound planetary gear set 15. The connecting gear 16 is also provided with a plurality of teeth 20 that allow the connecting gear 16 to serve as a sun gear in a second planetary gear set 21 of the compound planetary gear set 15. As such, the common connecting gear 16 simultaneously serves as a ring gear and as a sun gear. With reference to the first planetary gear set 19, the teeth 18 which allow the common connecting gear 16 to serve as a ring gear meshingly engage a plurality of pinion or planetary gears 22 that are connected by a carrier 23. The planetary gears 22 are also meshingly engaged with a sun gear 24. Thus, the sun gear 24, the planetary gears 22 mounted on the carrier 23 and the teeth 18 which serve as the ring gear portion of the common connecting gear 16 constitute the first planetary gear set 19. With reference to the second planetary gear set 21, the teeth 20, which allow the common connecting gear 16 to serve as sun gear in the second planetary gear set 21, meshingly engage a plurality of pinion or planetary gears 25 that are connected by a carrier 26. The planetary gears 25 are also meshingly engaged with a ring gear 28. Thus, the teeth 20 which allow the common connecting gear 16 to serve as a sun gear, the planetary gears 25 mounted on the carrier 26 and the ring gear 28 constitute the second planetary gear set 21. It should also be observed that the ring gear 28 on the second planetary gear set 21 is permanently connected to the internal combustion engine 11, as represented by line 27 in Figure 1. A damper, not shown, may be added between the ring gear 28 and the engine 11 to reduce engine torque pulsations. The sun gear 24 in the first planetary gear set 19 is permanently connected to the rotor 12 of the electric motor/generator 14, such that those two structural elements of the power transmission 10 will only rotate in unison. This connection is represented by line 29 in Figure 1. The carrier 23 of the first planetary gear set 19 is selectively connected to ground 30 through a torque transfer device in the nature of a brake 31. A one-way clutch 32 is interposed between the carrier 23 and ground 30 in order to assure that the carrier 23 can only rotate in one direction. The common connector gear 16 is engaged solely by the planetary gears 22 and 25 of the first and second planetary gear sets 19 and 21, respectively. The carrier 26 in the second planetary gear set 21 is selectively connectable to the rotor 12, as through a first torque transfer device in the nature of a clutch 33. The carrier 26 is also selectively connectable to the ring gear 28 of the second planetary gear set 21 through a second torque transfer device, in the nature of a clutch 34. The carrier 26 is, in addition, permanently secured to an output sleeve shaft, represented by line 37 in the drawings. The sleeve shaft 37 is connected to a pulley 35 which constitutes the output member by which torque is transferred -- as by a chain drive 36 -- from the integrated hybrid power transmission 10 to an input pulley 38. The input pulley 38 is presented from a standard drive ratio selection transmission 39 that may also incorporate one or more planetary gear sets, as is well known to those skilled in the art. As is also conventional, the drive ratio selection transmission 39 may be connected, as through a differential 40, to the final drive shafts or axles 41A and 41B of the vehicle, not shown, in which the power transmission 10 is utilised. Finally, the pulley 35 -- to which the carrier 26 of the second planetary gear set 21 in the power transmission 10 is permanently secured -- is itself selectively connected to ground 30 through a torque transfer device in the nature of a brake 42. Because of the complexity of planetary gear systems -- and their associated components -- when incorporated in vehicle transmissions, transmission engineers and designers have developed and employ a schematic convention called "stick diagrams" to represent a "lever analysis" by which to facilitate the depiction and an understanding of how particular transmissions, even those which employ complex planetary gear sets, operate. The diagrammatic lever analysis provided by these stick diagrams are readily developed into free body diagrams, the essential tool of mechanical analysis. As such, the operation of the present power transmission 10 will now be presented with the assistance of the stick diagrams set forth in Figures 3 to 9. In the lever analysis depicted in Figures 3 to 9 the compound planetary gear sets 19 and 21 are represented by levers bearing the same numerical identification, and the common connecting gear 16 to those two planetary gear sets is represented by the rigid connecting link 16 that extends between the point 18 on lever 19 and point 20 on lever 21. This depiction, therefore, represents the common connecting gear 16 that presents the ring gear teeth 18 for the first planetary gear set 19, as well as the sun gear teeth 20 for the second planetary gear set 21. The rotor 12 of the electric motor/generator 14 is represented as being permanently connected, as by the link 29, to the point 24 of the lever 19 (that is, the first planetary gear set) that represents the sun gear. The carrier is represented by point 23 on lever 19, which is connected to ground 30 not only through the one-way clutch 32 but also through the (selectively operable torque transfer) brake 31. With the second lever 21 representing the second planetary gear set, the point 28 represents the ring gear that is connected to the internal combustion engine 11 by the rigid link 27. The carrier of the second planetary gear set 21 is represented by point 26 on the lever 21. The carrier 26 is also represented as being connected to ground 30 through (torque transfer) brake 42, as well as to the drive ratio selection transmission, as represented by output pulley 35. It should also be understood that the electric motor/generator 14 may be controlled through the use of a system such as that described in US Patent No. 4,883,973. Engine Start Mode Referring to Figure 3, a lever analogy for the power transmission 10 is presented to depict starting the internal combustion engine 11 by the torque applied from the electric motor/generator 14. Both the carriers 23 and 26 are grounded through the respective torque transfer devices 31 and 42. This may be accomplished by simultaneously actuating the brakes 31 and 42 by virtue of a park lever, as represented by the dashed lines 45. By thus grounding the carriers 23 and 26, a reactive speed ratio may be established between the electric motor/generator 14 and the crankshaft of the internal combustion engine 11. The crankshaft may be schematically represented by the connecting line 27 that extends between the internal combustion engine 11 and the ring gear 28. By appropriate selection of the relative numbers of teeth on the sun and ring gears in each planetary gear set 19 and 21, a reactive speed ratio on the order of approximately 4:1 may be established. This ratio dictates the electric motor/generator torque. A silent start may be attained with this arrangement. Obviously, the internal combustion engine 11 can only be started in this manner when the Park or Neutral Mode of the power transmission 10 is employed. High generator output is also available in the Park or Neutral Mode. Prevention of gear rattle and a reduction in crank shaft pulsations may also be obtained by the provision of some reactive torque by the electric motor/generator 14. When employing an oil pump not driven by the internal combustion engine 11, brake 48, as shown in Figure 4, and automatic transmission brakes and clutches (torque transfer devices that ground the transmission input) may be actuated in Park or Neutral Mode for engine start. Automatic transmission operation with the power transmission 10 is effected by shifting from the Park or Neutral Mode to a Drive Mode. It should also be appreciated that the generator field is reduced for shift feel when the carriers 23 and 26 are freed from ground by manipulation of the park lever 45. Vehicle Launching Mode With the engine running, and in Launching Mode, the flywheel inertia of ring gear 28 and the attached components react in both positive and negative directions with the crankshaft. The flywheel inertia of rotor 12 of the electric motor/generator 14 and the attached components react only in the positive or forward direction through one-way clutch 32, thereby requiring less energy to maintain the engine speed while reducing idle shake. With specific reference to Figure 4, a lever analogy for the power transmission 10 is presented to depict launching of the vehicle. Two methods of launch may be used. The first -- designated as the heavy throttle inertia-assisted method -- uses the (torque transfer device) clutch 33 as a starting clutch. For example, with the internal combustion engine 11 operating at 600 RPM and the rotor 12 of the electric motor/generator 14 revolving at 2,300 RPM -- a 3.86 ratio -- the accelerator is depressed. Reaction is through the one-way clutch 32 to ground 30. The internal combustion engine 11 is operated in a manner that would effect acceleration of the vehicle. The electric motor/generator 14 would also be accelerated. However, the clutch 33 is applied to decelerate the electric motor/generator 14 at a controlled rate. The internal combustion engine 11 maintains its speed and the torque resulting from the inertia of the rotor 12 is added to the torque applied by the internal combustion engine 11 during initiation of the launch. As the differential speed across the clutch 33 decreases, the torque of the electric motor/generator 14 is increased to maintain a controlled rate of application to synchronous speed lock up. The second or alternative method of launching a vehicle with the power transmission 10 is designated as the light to mid-throttle generator reaction launch. The light to mid-throttle generator reaction launch is accomplished by directing the launch reaction through the one-way clutch 32 to ground 30 and by controlling the speed by the electric motor/generator 14 through an electric brake reaction to ground 30. With the internal combustion engine 11 operating at 600 RPM and the rotor 12 of the electric motor/generator 14 revolving at 2,300 RPM, the accelerator is depressed. The reaction is through the one-way clutch 32 to ground 30, and the internal combustion engine 11 is operated in a manner that would effect acceleration of the vehicle. This would normally accelerate rotation of the electric motor/generator 14. However, deceleration is provided by reversing the field of the stator 13, thereby causing the electric motor/generator 14 to act as an electric brake. This motor/generator reaction serves to charge the battery and also controls the rate at which the vehicle is accelerated. In this way, it is possible to effect the desired acceleration with decreased throttle application in order to provide maximum economy of operation and to achieve the desired emission reduction, during the launch phase. The clutch 33 may be applied at or near the synchronous speed and the motor/generator torque adjusted for the most desirable interaction. It should also be appreciated that a bridging torque transfer device in the nature of brake 48 may be added in parallel with the one-way clutch 32 to provide an alternative means by which to effect torque reversal -- that is, to simulate electric field reversal and to effect regenerative braking -- when the clutch 33 is not applied. That is, the rotor 12 of the electric motor/generator 14 rotates in the same direction as the internal combustion engine 11, and at a speed three to four times greater that the speed of the internal combustion engine 11 when the vehicle is stopped. This relative speed differential provides reaction for launch of the vehicle and inertia for virtually eliminating the undesirable jerking that might otherwise be felt when the clutch 33 is actuated. Motor/Generator Coupling Mode Referring to Figure 5 a lever analogy for the power transmission 10 is presented to depict the motor/generator coupling phase after the clutch 33 is engaged and the output torque ratio is increased, as for example, from 1.5:1 to 1.7586:1 times the torque supplied by the internal combustion engine 11. In this condition, the torque of the electric motor/generator 14 may be added or subtracted from the multiplied torque of the internal combustion engine 11. The resulting axial torque controlled by the electric motor/generator 14 assures the desired best performance by selectively optimising the operation of the internal combustion engine throttle opening for best fuel economy and desirable emissions. Internal Combustion Engine Coupling Mode Referring to Figure 6, the lever analogy for the power transmission 10 is presented to depict the condition of the compound planetary gear set 15 with the application of the engine torque transfer device (clutch) 34. The torque ratio changes from 1.786:1 to 1:1 times the engine torque. During this ratio change, and all subsequent transmission ratio changes, the electric motor/generator 14 may be used to bias the axial torque before, during and after the shifting or application of the clutch 34, resulting in less disturbance. Regeneration Mode Referring to Figure 7 the lever analogy for the power transmission 10 is presented to depict the regeneration mode -- that is, the mode whereby energy may be recovered when operating with the clutch 34 disengaged during deceleration and with the clutch 33 engaged so that the electric motor/generator 14 remains coupled to the output sleeve shaft 37 -- which remains coupled to the final drive shafts, or axles, 41 -- for maximum energy recovery. The speed of the internal combustion engine 11 may be reduced. However, the speed of the internal combustion engine 11 may have to be increased in order to assist the electric motor/generator 14 should the driver seek to accelerate the vehicle. The present power transmission 10 makes two torque ratios available when operating in the Regeneration Mode. For example, if the speed of the internal combustion engine 11 is increased, the one-way clutch 32 will react to ground 30 and -- with the same relative number of teeth on the sun and ring gears in the planetary gear sets 19 and 21 as heretofore assumed -- a power ratio of 1.7586:1 will be automatically provided. On the other hand, if the clutch 34 is reapplied, a ratio of 1:1 will result. During deceleration, the system operation is determined by driver input as well as the state of the battery charge. If a maximum charge is required, the power transmission 10 will drive the electric motor/generator 14 for the maximum output. If a minimum charge is required, the power transmission 10 will drive the electric motor/generator 14 at the optimum torque range before the system blends in the service brakes. In the event that the service brake time or temperature becomes excessive, the clutch 34 would engage to provide engine braking. Motor/Generator Only Mode Only limited performance is available when driving the vehicle through the power transmission 10 solely by the electric motor/generator 14, as represented by the lever analogy presented in Figure 7. However, an electric oil pump (not shown) may be added to actuate the clutch 33. Alternatively, as depicted in Figure 8, a second one-way clutch 49 may be added. When the second one-way clutch 49 is added and the clutch 34 is applied, the motor/generator torque is increased by 1.933, and better performance results. However, engine braking and starting is lost in this configuration unless a torque transfer device in the nature of a bridging clutch 50 is added to span across the one-way clutch 49. In this mode, the electric motor/generator 14 is operated in a reverse direction and a reverse gear must be provided in the drive ratio selection transmission 39 to reverse the vehicle direction. Manual Transmission Options The above-described power transmission 10 may also be used with manual ratio control systems. Starting the internal combustion engine 11 with a manual drive ratio system is the same as with an automatic drive ratio system. That is, both carriers 23 and 26 must to be grounded for reaction. During the Motor/Generator Coupling Mode and the Internal Combustion Engine Coupling Mode, operation with a manual drive ratio selection transmission is the same as with an automatic drive ratio selection transmission. Once both the clutch 34 and the clutch 33 are applied, two methods of manual shifting are available. With the first method, both the clutch 34 and the clutch 33 are switched over to manual clutch pedal control, and gear synchronisation may be achieved with synchronisers well known to those skilled in the art. Alternatively, the clutch 34 may be switched over to pedal control. When the clutch 34 is pedal actuated and the clutch 33 is engaged, the electric motor/generator 14 provides precise control over the speed of the power transmission 10 output sleeve shaft 37. However, when the shift lever of the manual drive ratio selection transmission is moved into the next drive select gate, the electric motor/generator 14 is regulated to provide the synchronous speed necessary for the drive ratio selected. By eliminating the transmission synchronisers the cost of the input differential may be offset. Another alternative manual transmission method during launch includes providing sequential manual control of first, the clutch 33 and sequentially thereafter the clutch 34. Using the power transmission 10 in the Regeneration Mode may be accomplished with a manual drive ratio selection transmission in the same manner as previously described herein for the automatic drive ratio selection transmission. Operation in the Motor/Generator Only Mode with the manual drive ratio selection transmission may be provided during launch from a stopped condition with the electric motor/generator 14, but with the clutch 33 applied. Alternatively, the electric motor/generator 14 may be rotated with the clutch 33 manually applied to utilise the torque supplied by the inertia of the rotor 12 of the electric motor/generator 14 and any associated flywheel. Releasing the clutch 33 may be necessary for changing gears, if total synchronisation is not possible. Also, a reverse transmission gear would be required to reverse the vehicle. It should be understood that in normal cruising operation, the internal combustion engine 11 is the prime power source and the electric motor/generator 14 provides additional power for vehicle demands, such as passing without gear change and going up hill. The electric motor/generator 14 also is controlled for providing the desired battery charge by recovering power as the vehicle is going down hill and/or decelerating. Controls may also be utilised to manipulate the internal combustion engine throttle for best fuel economy and improved engine emissions. Electric Reverse Operation With reference to Figure 9, it can be observed that a bridging torque transfer device in the nature of a clutch 51 provides a means for effecting complete disconnection of the internal combustion engine 11 from the power transmission 10. Reverse drive operation is provided by engaging both clutch 34 and brake 48 and selecting a forward ratio, preferably first gear, in the drive ratio selection transmission 39. Thus, if the internal combustion engine 11 becomes inoperable, the vehicle can be moved by utilising the electric motor/generator 14. Conclusion From the foregoing description, it should be readily apparent to those skilled in the art that a power train for automotive vehicles is provided utilising an electric motor/generator, planetary gear sets and clutches which can be controlled for optimum start, launch, acceleration and deceleration conditions with automatic and manual drive ratio selection transmissions.

Claims: A power transmission (10) for a vehicle having an internal combustion engine (11), a motor/generator (14) and a drive ratio selection transmission (39), the power transmission comprising compounded first and second planetary gear sets (19,21), each having a sun gear (24,20), and a plurality of planetary gears (22,25); characterised in that the first and second planetary gear sets (19,21) each further have a ring gear (18,28); in that the plurality of planetary gears (22,25) are mounted on carriers (23,26) operatively to connect the sun and ring gears of the respective first and second planetary gear sets; by a common gear member (16) serving not only as the ring gear for the first planetary gear set but also as the sun gear for the second planetary gear set; by means (34) capable of selectively transferring torque from the internal combustion engine to the carrier and ring gear of the second planetary gear set; by means (33) capable of selectively transferring torque between the motor/generator and the sun gear of the first planetary gear set and the carrier of the second planetary gear set; by means (33,34) capable of selectively transferring torque to and from the drive ratio selection transmission and the internal combustion engine, the ring gear of the second planetary gear set and the motor/generator through the carrier of the second planetary gear set; by means (31) capable of selectively connecting the carrier of the first planetary gear set to ground (30); and by means (42) capable of selectively connecting the drive ratio selection transmission to ground. A power transmission as claimed in Claim 1, wherein the means to selectively transfer torque between carrier (26) of the second planetary gear set (21) and the motor/generator (14) comprises a clutch (33). A power transmission as claimed in Claim 1 or Claim 2, wherein the means selectively to transfer torque from the internal combustion engine (11) to the carrier (26) and ring gear (28) of the second planetary gear set (21) comprises a clutch (34) which effects selective connection between the carrier of the second planetary gear set and the ring gear of the second planetary gear set. A power transmission as claimed in any one of Claims 1 to 3, wherein the means selectively connecting the carrier of the first planetary gear set to ground (30) comprises a brake (31); and wherein the means selectively connecting the drive ratio selection transmission (39) to ground comprises a brake (42) which selectively connects the carrier (26) of the second planetary gear set (21) to ground. A power transmission as claimed in Claim 4, further comprising means (45) to effect simultaneous actuation of the brakes (31,42). A power transmission as claimed in Claim 4 or Claim 5, further comprising a selectable one-way clutch (32) interposed between the carrier (23) of the first planetary gear set (19) and ground (30) for effecting utilisation of a positive flywheel inertia. A power transmission as claimed in Claim 6, further comprising a torque transfer brake device (48) spanning the one-way clutch (32) to selectively connect the carrier (23) of the first planetary gear set (19) to ground (30). A power transmission as claimed in Claim 6 or Claim 7, further comprising a second one-way clutch (49) interposed between the ring gear (28) of the second planetary gear set (21) and the internal combustion engine (11). A power transmission as claimed in Claim 8, further comprising a torque transfer clutch device (50) spanning the second one-way clutch (49) selectively to connect the ring gear (28) of the second planetary gear set (21) to the internal combustion engine (11).

Inventors: SHERMAN JAMES FRANCIS, SHERMAN, JAMES FRANCIS
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: B60K6
IPC codes: F16H37, B60W10, B60K6, B60L11, B60K17, B60W20, F16H3